/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * kernel/pthread/pthread_mutexlock.c
 *
 *   Copyright (C) 2007-2009 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <unistd.h>
#include <pthread.h>
#include <sched.h>
#include <assert.h>
#include <errno.h>
#include <debug.h>

#include <tinyara/sched.h>

#include "pthread/pthread.h"

/****************************************************************************
 * Definitions
 ****************************************************************************/

/****************************************************************************
 * Private Type Declarations
 ****************************************************************************/

/****************************************************************************
 * Global Variables
 ****************************************************************************/

/****************************************************************************
 * Private Variables
 ****************************************************************************/

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: pthread_mutex_lock
 *
 * Description:
 *   The mutex object referenced by mutex is locked by calling
 *   pthread_mutex_lock(). If the mutex is already locked, the calling thread
 *   blocks until the mutex becomes available. This operation returns with the
 *   mutex object referenced by mutex in the locked state with the calling
 *   thread as its owner.
 *
 *   If the mutex type is PTHREAD_MUTEX_NORMAL, deadlock detection is not
 *   provided. Attempting to relock the mutex causes deadlock. If a thread
 *   attempts to unlock a mutex that it has not locked or a mutex which is
 *   unlocked, undefined behavior results.
 *
 *   If the mutex type is PTHREAD_MUTEX_ERRORCHECK, then error checking is
 *   provided. If a thread attempts to relock a mutex that it has already
 *   locked, an error will be returned. If a thread attempts to unlock a
 *   mutex that it has not locked or a mutex which is unlocked, an error will
 *   be returned.
 *
 *   If the mutex type is PTHREAD_MUTEX_RECURSIVE, then the mutex maintains
 *   the concept of a lock count. When a thread successfully acquires a mutex
 *   for the first time, the lock count is set to one. Every time a thread
 *   relocks this mutex, the lock count is incremented by one. Each time the
 *   thread unlocks the mutex, the lock count is decremented by one. When the
 *   lock count reaches zero, the mutex becomes available for other threads to
 *   acquire. If a thread attempts to unlock a mutex that it has not locked or
 *   a mutex which is unlocked, an error will be returned.
 *
 *   If a signal is delivered to a thread waiting for a mutex, upon return
 *   from the signal handler the thread resumes waiting for the mutex as if
 *   it was not interrupted.
 *
 * Parameters:
 *   mutex - A reference to the mutex to be locked.
 *
 * Return Value:
 *   0 on success or an errno value on failure.  Note that the errno EINTR
 *   is never returned by pthread_mutex_lock().
 *
 * Assumptions:
 *
 * POSIX Compatibility:
 *   - This implementation does not return EAGAIN when the mutex could not be
 *     acquired because the maximum number of recursive locks for mutex has
 *     been exceeded.
 *
 ****************************************************************************/

int pthread_mutex_lock(FAR pthread_mutex_t *mutex)
{
	int mypid = (int)getpid();
	int ret = EINVAL;

	svdbg("mutex=0x%p\n", mutex);
	DEBUGASSERT(mutex != NULL);

	if (mutex != NULL) {
		/* Make sure the semaphore is stable while we make the following
		 * checks.  This all needs to be one atomic action.
		 */

		sched_lock();

#ifdef CONFIG_PTHREAD_MUTEX_TYPES
		/* All mutex types except for NORMAL (and DEFAULT) will return
		 * and an error  error if the caller does not hold the mutex.
		 */

		if (mutex->type != PTHREAD_MUTEX_NORMAL && mutex->pid == mypid) {
			/* Yes.. Is this a recursive mutex? */

			if (mutex->type == PTHREAD_MUTEX_RECURSIVE) {
				/* Yes... just increment the number of locks held and return success */

				if (mutex->nlocks < INT16_MAX) {
					mutex->nlocks++;
					ret = OK;
				} else {
					ret = EOVERFLOW;
				}
			} else {
				/* No, then we would deadlock... return an error (default behavior
				 * is like PTHREAD_MUTEX_ERRORCHECK)
				 */

				sdbg("Returning EDEADLK\n");
				ret = EDEADLK;
			}
		} else 
#endif /* CONFIG_PTHREAD_MUTEX_TYPES */


#ifndef CONFIG_PTHREAD_MUTEX_UNSAFE
		/* The calling thread does not hold the semaphore.  The correct
		 * behavior for the 'robust' mutex is to verify that the holder of the
		 * mutex is still valid.  This is protection from the case
		 * where the holder of the mutex has exitted without unlocking it.
		 */

#ifdef CONFIG_PTHREAD_MUTEX_BOTH
#ifdef CONFIG_PTHREAD_MUTEX_TYPES
		/* Include check if this is a NORMAL mutex and that it is robust */

		if (mutex->pid > 0 &&
			((mutex->flags & _PTHREAD_MFLAGS_ROBUST) != 0 ||
			mutex->type != PTHREAD_MUTEX_NORMAL) &&
			sched_gettcb(mutex->pid) == NULL)
#else /* CONFIG_PTHREAD_MUTEX_TYPES */
		/* This can only be a NORMAL mutex.  Include check if it is robust */

		if (mutex->pid > 0 &&
			(mutex->flags & _PTHREAD_MFLAGS_ROBUST) != 0 &&
			sched_gettcb(mutex->pid) == NULL)
#endif /* CONFIG_PTHREAD_MUTEX_TYPES */
#else /* CONFIG_PTHREAD_MUTEX_ROBUST */
		/* This mutex is always robust, whatever type it is. */
		if (mutex->pid > 0 && sched_gettcb(mutex->pid) == NULL) 
#endif
		{
			DEBUGASSERT(mutex->pid != 0);	/* < 0: available, >0 owned, ==0 error */
			DEBUGASSERT((mutex->flags & _PTHREAD_MFLAGS_INCONSISTENT) != 0);

			/* A thread holds the mutex, but there is no such thread.  POSIX
			 * requires that the 'robust' mutex return EOWNERDEAD in this case.
			 * It is then the caller's responsibility to call pthread_mutx_consistent()
			 * fo fix the mutex.
			 */

			mutex->flags |= _PTHREAD_MFLAGS_INCONSISTENT;
			ret = EOWNERDEAD;
		} else 
#endif /* !CONFIG_PTHREAD_MUTEX_UNSAFE */
		{

			/* Take the underlying semaphore, waiting if necessary.  NOTE that
			 * is required to deadlock for the case of the non-robust NORMAL or
			 * default mutex.
			 */

			ret = pthread_mutex_take(mutex, true);

			/* If we succussfully obtained the semaphore, then indicate
			 * that we own it.
			 */

			if (ret == OK) {
				mutex->pid = mypid;
#ifdef CONFIG_PTHREAD_MUTEX_TYPES
				mutex->nlocks = 1;
#endif
			}

		}

		sched_unlock();
	}

	svdbg("Returning %d\n", ret);
	return ret;
}
